We have continued our studies of transcriptional regulation via antitermination in prokaryotes. Our studies have focused on the protein:protein and protein:RNA interactions associated with the NusB and NusE proteins and the boxA RNA. We have determined the solution structure of NusB from Aquifex aeolicus, shown it to be consistent with all NusB homologues, and investigated the biophysics of NusB:NusE interactions. These studies have revealed the binding site of NusE on NusB and provide an explanation for the increased affinity for boxA RNA binding to the binary NusB:NusE complex compared to boxA RNA:NusB binding. This work is under revision for publication in the Journal of Molecular Biology. Additionally, the solution structure of the E. coli NusB:boxA RNA binary complex is nearly completed. This complex reveals new insight into the ternary complex of NusB:NusE:boxA RNA. These studies are enhanced by analyses of the binding interactions for various known mutations of NusB. The overall study will enable a more detailed and global picture of the interactions critical to the process of antitermination than have been available before.